Classic Computer Magazine Archive COMPUTE! ISSUE 143 / AUGUST 1992 / PAGE 50

Organize your disk with FDISK. (Column)
by Tony Roberts

DOS's FDISK is the utility that's used to examine and change hard disk partition information. FDISK doesn't get the kind of everyday use that commands like DIR and TYPE get, but it has its purposes.

In earlier versions, DOS was able to access only hard disk partitions of 32 megabytes or less in size. DOS 4.01 and DOS 5.0 have eliminated that barrier, permitting hundreds of megabytes of hard disk storage in a single partition.

Although this appears to be an advantage, there are good reasons for breaking a large hard disk into smaller segments. You may want to isolate game files from business files, or Bob's files from Mary's. If you have a large hard disk that needs partitioning--or a partitioned hard disk that you'd like reorganized--FDISK is the tool to use.

First, be warned that FDISK is a powerful utility. It's designed to give you a clean state--to wipe out everything on your hard disk. Before you undertake any FDISK experimentation, make sure you have a full and verified backup of all your hard disk's data.

Also, make sure you have plenty of time. Repartitioning a hard disk requires backing up the data, repartitioning, formatting the new partitions, and then restoring all the data.

FDISK is careful, though, about not destroying information without demanding your confirmation. You can run FDISK and display partition information, for example, without being concerned about wiping out your disk.

Let's say that you want to partition your hard disk into three logical drives--C:, D:, and E:. Make your backups and create a boot-up disk that includes the operating system files as well as FORMAT, FDISK, CHKDSK, and whatever programs you'll need to restore your backups. Then run FDISK.

Let's assume that we have a 100-megabyte disk that needs to be partitioned into these areas: 50 megabytes for C:, 25 megabytes for D:, and 25 megabytes for E:. Start by selecting the Delete option to remove the current partitions. This will render the data on your hard disk useless, so double-check those backups.

Once all the partitions are deleted, choose the option to create a primary DOS partition. This is the partition that will contain your DOS startup files--your boot drive. When you're asked whether this partition should be made the maximum possible size, answer no. Select a 50-megabyte partition. The partition you've just created will be known as drive C:, the name given to the primary partition on the first hard disk in any system.

Follow the FDISK menu selections to create an extended DOS partition. FDISK will suggest using all of the remaining space for the extended partition, and you should agree. Even though you're going to create two more logical drives, you're permitted to create only one extended DOS partition per drive.

Once the extended DOS partition is created, you can choose the option to create logical drives. You can have as many as 23 logical drives, but all the logical drives you create will exist within the one extended DOS partition. Specify sizes for the logical drives, and FDISK will assign a drive letter in sequence to each logical drive you create.

Once the disk is partitioned, there's one final step to take. You must use option 2 from the main FDISK menu--Set Active Partition--to make your primary DOS partition active. This is crucial; without it, you won't be able to boot from the hard disk.

When all the changes are made, exit FDISK, restart the system from the startup floppy, and reformat each of your new drives. Use the FORMAT command with the system switch (FORMAT C:/S) to copy the system files to the C: drive and to make it bootable. Then format the other drives normally.

After formatting, restore your programs and data files from the backups, and you're in business. If you add a second hard drive to your system, be prepared for some confusion with logical drive names on your first hard disk's extended DOS partition.

As I mentioned earlier, the primary DOS partition on the first hard disk is always designated with the C: label. Similarly, a primary DOS partition on a second hard disk is always designated with the D: label. If your first hard disk originally included logical drives D: and E:, those designators will be changed to E: and F: when the D: designator is assigned to the primary DOS partition on the second drive.

This change in drive designators will cause you to rework any batch files, scripts, or program startup icons that refer to the original names.

You can avoid this problem of logical drive name switching by not creating a primary DOS partition on the second hard disk. Just create an extended DOS partition and fill it up with as many logical drives as you want. These new storage areas will be given names that follow the names of the logical drives on the first hard disk.

It isn't easy to repartition a hard drive. It's worth doing if the resulting setup will make it easier for you to do your work or protect your data.